Temperature controller for an adiabatic vessel



July 15, 1958 L. s. STANTON TEMPERATURE CDNTROLLER FOR AN ADIABATIC VESSEL Filed Sept. 18, 1956 ATTORNEYS United States iPatent O TEMPERATURE CONTROLLER FOR AN ADIAIEATKC VESSEL Lyman S. Stanton, Novato, Calif., assigner to California Research Corporation, Sanl Francisco, Calif., a corporation of Delaware Application September 18, 1956, Serial No. 610,514

4 Claims. (Cl. 219--20) r[his invention relates to an apparatus for temperature control throughout an 'insulated distillation, contacting or reaction vessel, and specically refers to means for sequentially comparing the temperatures within predetermined zones along the length of the vessel with the corresponding temperatures of the shell enclosing `said zones, and for controlling the localized input of heat into the zones to maintain a minimum temperature difference or adiabatic condition, so that operations carried out in the vessel will occur without gain or loss of heat from each'zone.

The' specic example of the invention illustrated and described herein is applied to a conventional fractional distillation column, insulated against excessive loss of heat to the atmosphere and outwardly'divided into a plurality of longitudinally spaced sections, each provided with a separate heating element, such asawinding of resistance wire. A vfirst thermocoupley orv other temperature-responsive element is placed in contactwith the column shell substantially at the center of the zone enclosed by` each section, and a second element is placedinside the column opposite the rst one, to be responsive to the Vapor or other fluid temperature within that zone. A comparator is connected to the inner and outer thermocouples ofeach zone in sequence and its output controls the energizing of the respective heaters by a system of synchronized multiposition contactors and relays which maintain the minimum diierence between the temperatures, as will be more fully explained below.

This example is illustrated diagrammatically in the accompanying drawing, in whcih a portion of the fractionating column, arranged for adiabatic operation, is shown in a simplified vertical sectional view, and the electrical and timing control system is shown schematically.

Referring to the drawing, reference numeral designates generally the elongated vertical shell of a Kconventional fractionating column provided with packing such as the usual vertically spaced plates 11 and bubble caps 12. For convenience, these are illustrated only in the lower part of shell 10, but it is understood that they may extend substantially throughout its length. Outside the shell 10 is suitable insulation 13, illustrated as being sectionalized into vunits I, II, and III, and adapted to retard the flow of heat to the atmosphere from the corresponding zones I, II, and III inside the column. The temperatures in the several zones are generally different, in the case of the usual fractionating column having a temperature gradient that increases downwardly, so that zone III is hotter than zone II, for example, for reasons well known in this art. Connections for admission and removal of liquids and vapors are not illustrated, as they form no part of this invention. However, it is understood that reflux liquid ows downwardly and vapors to be separated ow upwardly in the column and pass through the several zones I, II, and III in which adiabatic conditions are desired to be maintained.

Outside of each zone is a heating unit such as a winding of high resistance wire, designated heaters I, II, and III,

Patented July 15, 1958 respectively, and adaptedto add heat to that section of column 10 which it surrounds. A first temperatureresponsive elementsuc'h as a thermocouple 14 is positioned outside of the shell of column 10 opposite zone I. Within that zone, inside of `shell10, is a second thermocouple 15,' responsive to the iluid temperature at that point. The successive sections II, III, etc. are similarly provided with outer-andlinner pairs vof thermocouples, designated in'this example 16-17 and 18-19.

In order toycorn'pare the response of thermocouples 14 and 15 to determine IWhether the inside of zone I is hotter or colder than shell 10 at that point, wires 20 and 21, illustrated singly instead ofin pairs to simplify the diagram, lead to appropriate contacts of a` thermocouple scanning switch generallyl designated 22, provided with inner and, outer rings 23 and 24, which are in turn connectedvbywires 25 andf26 to a thermocouple comparator y27 which; may be a conventional potentiometer or millivoltmeter. The-output signal of comparator 27 is conducted'through Wires 28"and 29 to the winding 30 of rst relay A. Inthis example, if the inner or second thermocouple 15 is'at a'higher temperature than the outer, or first thermocouple 14, which would require addition of heat tothe shell10 of zone I to restore adiabatic conditions therein, relay A 'would bevv energized to close its contacts 31,r thus connectingV the source 32 of electric energy tothe heater switch 33 by means to be described. This latter 'switch is similar in construction to the thermocouple scanning switch 22'and is driven in synchronism with it by a timing motor generally designated 34and a common shaft" 35.' Desirably, but not necessarily, the motor does v not rotate continuously, but advances the contact arms of 2Z'and33stepwise from one set of contacts to the next, with'an appropriate dwell period at eachposition. In one embodiment of the invention the six positions of the scanning switch were contacted once each minute. p

Heater`switch'33, like thermocouple switch 22, is illustrated as having an inner ring'36 and outer ring 37, connected, respectively, to`- contact 31 yoflirst relay A and to a synchronized, normally open cam switch 38, also actuated from timing motor 34, through means such as gears 39 and cam 40 each time that switches 33 and 22 are advanced from one set to a succeeding set of contacts. Inner and outer contacts l through 6, inclusive, of heater switch 33 are connected to the several heater units I, II, III, etc. of the column shell 10, as will be described in detail below.

Referring now to the first heater I, surrounding zone I and thermocouples 14 and 15, wire 41 connects the outer contact 1 of switch 33 through the winding 4Z of a second relay B-l to one terminal of heater I. Wire 43 connects the inner contact 1 of switch 33 through one winding 44 of a third relay C-1 to the negative bus of electric power source 32. Relay C-1 is provided with normally open contacts 45 connected respectively by wires 46 and 47 to the positive bus of source 32 and to the other terminal of heater I. Thus, when the several switches 22, 33, and 38 are in the position shown, if the comparator 27 determines that the outer thermocouple 14 for the shell 10 at zone I is cooler than the inner thermocouple l5, relay A will close contacts 31, energizing relay C-1 to close its contacts 45 and thereby connect heater I to the electric power source 32, so that the shell temperature will be increased.

To maintain this condition until points l of switches 22 and 33 are next contacted, relay C-1 is provided with a holding winding 48 in series with a normally closed set of contacts 49 on relay B41, which will keep contacts 45 of relay C-1 closed. If the temperature of shell 10 at zone I should rise above that within the zone, thermocouple 14 will then have a larger output than thermccouple 15 at the time that switches 22 and 33 complete their cycle and next reach inner and outer contacts 1 corresponding to that zone. This time, relay A will remain open, under control of comparator 27, and when cam switch 38 is closed, relay B-1 will be energized, opening its contacts 49 and interrupting the holding winding 48 of relay C-l, thereby opening contacts 45 of that relay and disconnecting heater I from its source of electrical energy 32. This condition will remain until appropriate conditions of temperature difference again cause comparator 27 to initiate the sequence just described.

Thermocouples 16-17 and 18-19, as well as heaters II and III, for the corresponding zones in shell are similarly connected to correspondingly numbered sets of inner and outer contacts of switches 22 and 33, and are successively scanned and actuated by the thermocouple comparator 27, relay A, and cam switch 38 as just de* scribed for themocouples 14-15 of zone I. Although only two of such arrangements are illustrated in detail, it is obvious that they may be duplicated as desired.

In conclusion, it will be appreciated that this invention comprehends broadly means for sequentially comparing temperatures Within predetermined zones in a fractionating column, reactor, or the like with corresponding temperatures outside of those zones and for initiating and terminating the application of heat to those zones to maintain adiabatic conditions therein. Although a single example has been given of a preferred embodiment, it is understood that numerous modifications and changes could be made without departing from the invention, and all such that fall within the scope of the appended claims are intended to be embraced thereby.

I claim:

1. In combination with an elongated vessel having a plurality of separate longitudinally spaced heater units for maintaining an adiabatic condition inside said vessel, a rst means responsive to the temperature of the vessel shell inside one of said heater, a second means responsive to uid temperature Within said vessel, and substantially opposite said rst-named means, means for periodically comparing the response of said first and said second means, and means responsive to said comparison means for controlling the ow of energy to said heater unit.

2. In combination with an elongated vessel having a plurality of separate, longitudinally spaced heater units for maintaining an adiabatic condition inside said vessel, a tirst thermocouple responsive to the temperature of the vessel shell inside one of said heaters, a second thermocouple responsive to uid temperature within said vessel and substantially opposite said first thermocouple, means for periodically comparing the electrical potentials generated by said iirst and said second thermocouples, and means responsive to said comparison means for controlling the flow of energy to said heating unit.

3. A combination according to claim 2, in which said controlling means comprises a iirst relay adapted to be actuated when vapor temperature inside said vessel is higher than the shell of said vessel, a second relay responsive to said first relay for connecting said energy source to said heater, and a third relay adapted to actuate said second relay when the vapor temperature inside said vessel is lower than the temperature of the shell for interrupting the flow of energy to said heater unit.

4. In combination with an elongated vessel having a plurality of zones in each of which adiabatic conditions are to be maintained, a heater unit outside of each zone, a pair of horizontally aligned temperature responsive means for cach zone, one inside said zone and the other outside the shell of said vessel, means for periodically comparing the response of said pairs of temperature responsive units, and means responsive to said comparison means for controlling the flow of energy to each of said heater units.

References Cited in the le of this patent UNITED STATES PATENTS 1,222,492 Thomas Apr. 10, 1917 1,494,586 Cary May 20, 1924 1,511,050 Collins et al. Oct. 7, 1924 1,603,729 Wilhjelm Oct. 19, 1926 2,327,788 Hickman Aug. 24, 1943 2,379,675 Biebel July 3, 1945 2,598,036 Cahill et al. May 27, 1952 2,618,668 OConnor et al Nov. 18, 1952 

